INSIDIOUS Synonyms: 100 Similar and Opposite Words

insidious

adjective

Definition of insidious

as in treacherous

formal causing harm in a way that is gradual or not easily noticed Most people with this insidious disease have no idea that they are infected. an insidious enemy

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Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.

Recent Examples of insidious When his insidious nature is revealed, the change in tone and his face gone malformed, the scene feels dynamic in a way that doesn’t require gore or intricate special effects. — Literary Hub, 28 Aug. 2026 The broader opportunity costs of the United States’ Middle Eastern follies are even more insidious. — Emma Ashford, Foreign Affairs, 12 Aug. 2026 However, there is another, slower and more insidious evacuation taking place, and that is the steady migration from rural areas all around the world to burgeoning cities, which now host more than half the world’s population. — John Vaillant, Time, 8 Aug. 2026 This insidious method is a form of bullying, causing significant psychological harm and higher dissatisfaction than overt harassment. — Jason Walker Psyd, Forbes.com, 6 Aug. 2026 See All Example Sentences for insidious

Recent Examples of Synonyms for insidious

Adjective

International skullduggery in this case concerned the retrieving of two nuclear warheads from a treacherous Caribbean dictatorship.

— Ed Olmstead, HollywoodReporter, 17 Sep. 2026
Bryan, without chains on his tires, drives up a treacherous farm-country road in the snowy night, which lends the movie a fairy-tale atmosphere.

— Owen Gleiberman, Variety, 16 Sep. 2026

Definition of treacherous

Adjective

The comic tension embodies Cassavetes’ approach to the entire film, which involved some not-so-subtle manipulation of his actors behind the scenes.

— Jim Hemphill, IndieWire, 23 Sep. 2026
And just like her clothes and accessories serve as a subtle nod to the '90s, so does her beauty look.

— Marci Robin, Allure, 23 Sep. 2026

Definition of subtle

Adjective

That’s why Meta has agreed to pay up to eighteen billion dollars as part of a settlement over predatory and deceptive practices, and why Anthropic is paying writers and publishers (admittedly, pennies) in a copyright settlement.

— Jill Lepore, New Yorker, 21 Sep. 2026
Some states have enacted laws requiring disclosures or restricting deceptive political deepfakes near elections.

— Reed Williams, AJC.com, 21 Sep. 2026

Definition of deceptive

Adjective

In the wake of the 2020 election, false accusations led to death threats and upended the lives of two Fulton County election workers.

— Caleb Groves, AJC.com, 23 Sep. 2026
Election law generally requires registration in every state except North Dakota, while federal law prohibits false registration and other forms of election fraud.

— Los Angeles Times, Los Angeles Times, 23 Sep. 2026

Definition of false

Adjective

The final answer may cite real sources and still be misleading.

— Patrick Dajos, Forbes.com, 23 Sep. 2026
Providing false or misleading information to law enforcement undermines those efforts and unnecessarily diverts officers and resources away from members of our community who may need immediate police assistance.

— Brie Stimson, FOXNews.com, 19 Sep. 2026

Definition of misleading

Adjective

Bogus texts, mystery calls, deceitful emails all aimed at stealing your personal information and your money are relentless.

— Donna Vickroy, Chicago Tribune, 13 Aug. 2026
The mutual trust and goodwill that xenia sought to cultivate has been eroded by this one deceitful act, creating a world that is defined by this moral violation.

— Brianna Zigler, Entertainment Weekly, 19 July 2026

Definition of deceitful

Adjective

The agency produced excellent work against an incorrect brief, and nobody in the room knew the business well enough to say so.

— Expert Panel®, Forbes.com, 21 Sep. 2026
Oxford and Ole Miss rolled out the unwelcome mat early in the week, starting Wednesday with a Lane Kiffen (incorrect spelling intentional) Roast at the Lyric Theater.

— Dana O’Neil, CNN Money, 20 Sep. 2026

Definition of incorrect

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inside tracks

insidious

insidiously

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Style

“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 25 Sep. 2026.

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Synonyms of insidious

adjective

Example Sentences

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